1. Field of the Invention
Embodiments of the invention relate generally to methods for processing a substrate during semiconductor manufacturing. Specifically, embodiments of the invention relate to methods of treating a nucleation layer prior to a CVD deposition process.
2. Description of the Related Art
Reliably producing nanometer-sized features is one of the key technologies for the next generation of semiconductor devices. The shrinking dimensions of circuits and devices have placed additional demands on processing capabilities. The multilevel interconnects that lie at the heart of integrated circuit technology require precise processing of high aspect ratio features, such as vias and other interconnects. Reliable formation of these interconnects is very important to future success and to the continued effort to increase circuit density and quality of individual substrates.
Metallization of features formed on substrates includes CVD deposition of metals such as tungsten. Tungsten can be used for metal fill of source contacts, drain contacts, metal gate fill and gate contacts as well as applications in DRAM and flash memory. Growth of CVD tungsten from WF6 and H2 gas mixtures typically requires a pre-deposited underlayer of metallic tungsten to crack H2 into adsorbed atomic hydrogen and to initiate metal film growth.
In previous techniques, a tungsten nucleation layer is deposited from WF6 and SiH4 or WF6 and B2H6 on a barrier and adhesion layer of TiN or WN by an ALD process. However, this technique is rapidly losing extendability into less than 20 nm features due to the increasing volume fraction of the feature being consumed by the barrier metal and ALD-W nucleation.
Therefore, there is much effort in the art to create a tungsten deposition process which reduces the use of intermediate layers prior to bulk tungsten fill.